CDC, US and Brazilian researchers find evidence of onset of Zika-associated microcephaly and other neurologic complications after birth

Media Statement

For Immediate Release: Tuesday, November 22, 2016
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CDC researchers in collaboration with researchers from the United States and Brazil investigated the first series of infants with laboratory evidence of congenital Zika virus infection documented to have onset of microcephaly after birth.

The report, published today in CDC’s Morbidity and Mortality Weekly Report, describes 13 infants in Brazil with congenital Zika virus infection who did not have microcephaly at birth, but later experienced slowed head growth. Among these infants, 11 later developed microcephaly. Slowed head growth and microcephaly were accompanied by significant neurologic complications. Although microcephaly was not present at birth, the infants had other brain abnormalities consistent with congenital Zika syndrome.

The study reveals that among infants of mothers exposed to Zika virus during pregnancy, the absence of microcephaly at birth does not rule out congenital Zika virus infection or the presence of Zika-related brain abnormalities.

The findings highlight the importance of recent CDC guidance on initial and continuing medical and developmental evaluations of infants with possible congenital Zika virus infection and the importance of early neuroimaging for infants who were exposed to Zika virus prenatally.

CDC Guidance for Pregnant Women and Women Considering Pregnancy

CDC continues to recommend that pregnant women not travel to areas with Zika. If a pregnant woman travels to or lives in an area with active Zika virus transmission, she should talk with her healthcare provider and strictly follow steps to prevent mosquito bites and sexual transmission of Zika virus. Pregnant women with possible exposure to Zika virus should be tested for Zika infection even if they do not have symptoms. For more information, please visit

CDC continues to encourage women considering pregnancy and their partners in areas with active Zika transmission to talk to their healthcare providers about pregnancy planning so that they know the risks and the ways to reduce them. For more information, please visit


Page last reviewed: November 22, 2016